Controls for refrigeration apparatus



Feb. 1962 H. E. CASWELL ETAL 3,022,638

CONTROLS FOR REFRIGERATION APPARATUS Filed May 6, 1959 2 Sheets-Sheet 1 1 INVENTOR. G 2 HOWARD a. CASWELL BY JAMES w. enoaass ATTORNEY Feb. 27, 1962 H. E. CASWELL ETAL 3,022,638

CONTROLS FOR REFRiGERATION APPARATUS Filed May 6, 1959 2 SheetsSheet 2 FIG. 4

INVENTOR. HOWARD E. CASWELL By JAMES w. ENDRESS ATTORNEY United States Patent 3,022,638 CONTROLS FOR REFRIGERATION APPARATUS Howard E. Caswell, East Syracuse, and James W. Eu-

dress, Syracuse, N.Y., assignors to Carrier Corporation, Syracuse, N.Y., a corporation of Delaware Filed May 6, 1959, Ser. No. 811,463 4 Claims. (Cl. 62-115) This invention relates broadly to air conditioning apparatus. More particularly this invention relates to a refrigeration machine utilized in air conditioning apparatus. Still more particularly this invention relates to a control employed on a refrigeration machine of the type under consideration.

In air conditioning equipment of the type to which this invention pertains there is included a refrigeration machine employed to cool a medium which is delivered to an enclosure to be supplied with conditioned air. Very often the medium to be supplied to the enclosure is water which has its temperature increased as it flows through a closed circuit including individual units spaced throughout the enclosure. Located in heat transfer relation with a coil in the circuit is the evaporator of the refrigeration machine, for the purpose of absorbing the heat and reducing the temperature of the water. a

,y The refrigeration machine employed in the system described inpludestheusual components such as a compressor, condenser, economizer and evaporator connected to form a circuit for the flow of refrigerant in the conventional manner. In the case where the compressor in the machine described is of the centrifugal type, and includes a hermetic motor for driving the compressor, it has been found practical to utilize gaseous refrigerant from the economizer for the purpose of cooling the motor driving the compressor. As is well known, the economizer ,which in its broadest aspects may be described as reducing the pressure of the refrigerant flowing from the condenser to the evaporator in two stages, preparatory to its supply to the evaporator, has generated therein a supply of gaseous refrigerant through the commonly known flashing ofi process. In other words, when the refrigerant is reduced in pressure from the existing condenser pressure, a portion of the liquid refrigerant vaporizes, chilling the remaining liquid refrigerant and flowing either to the motor casing or directly to the compressor,

depending on the manner in which the motor driving the compressor is cooled. 7

Under certain operating conditions of the air con,-

ditioning apparatus, as for illustration, ,during periods .when the temperature of the ambient may fluctuate through a given twenty-four hour period, the'norrnal pressure differences maintained in the refrigeration system under operation are drastically changed. For example,

during the spring or fall season the ambient temperature which determines the temperature of the condensing medium used in the condenser may drop during the evening or ni ht hours. The enclosure being served by the air conditioning system may still have a requirement for cooling, due to the presence of an excessive number of persons within the enclosure or due to an excessive load such as lights or heat'generating equipment or machinery. Under Thus, liquid refrigerant tends to flow backward through the machine from the evaporator to the economizer and/or condenser. If the refrigeration machine being employed 3,922,533 Patented Feb. 27, 1952 ice in'the air conditioning-system utilizes a hermetic motor which is cooled by economizer gas, thereis a tendency for the liquid refrigerant in the economizer to flow through the path normally provided for the flow of gaseous refrigerant from the economizer to the motor casing, so that a strong possibility that liquid refrigerant will enter the motor casingexists. Liquid refrigerant within the motor casing may be harmful to the windings of the motor and further, at start-up, may, by virtue of a relatively low pressure existing in the motor casing, vaporize and carry with it portions of the lubricant main: tained in the motor casing. This can occur to such an extent that the control normally provided for terminating operation of the machine, due to low lubrication pressure, will interrupt operation of the machine to the discomfort of the occupants of the enclosure.

A related problem exists in equipment of the kind described wherein other means may be employed for cooling the motor and in equipment where it is not necessary to employ motor-cooling arrangements. In these instances the line for conducting gaseous refrigerant from the economizer connects directly to the compressor. A re verse flow of refrigerant in these machines may cause liquid refrigerantto be deposited ins the compressor increasing the power requirement of the machine at the time the machineis, operated initially.

The chief object of the invention is the provision of a control for a refrigeration machine of the kind under conside'ration'which is operative to prevent flow of refrigerant within the machine in a direction opposite the direction for which the flow is designed.

' A further object of the invention is the provision of a refrigeration machine control of the type described that is operative to vent the evaporator to a part of the refrigeration system which may, temporarily, have a pressure below that of the evaporator, although under normal design conditions that part would have a pressure in excess of the pressure in the evaporator.

Another object of this invention is the provision of a control for use in a refrigeration machine which is operative to sense abnormal pressure conditions within the evaporator and to vent the evaporator to the economizer so that either substantial equalization of pressure between the two elements of the machine occurs or the pressure in the economizer is supplemented so that the tendency of the liquid refrigerant in this system to flow from the evaporator is minimized.

Another object of the invention is a method of operating a refrigeration machine so that the tendency of liquid refrigerant to reverse its flow in the machine under circumstances Where abnormal pressurerelationships are encountered is minimized.

This invention in attaining the objects set forth con-'- templates a refrigeration system including a compressor, a condenser, an economizer and an evaporator connected to form a closed circuit, and means operable in response to a predetermined pressure relationship within the system for preventing reverse flow of refrigerant from the evaporator to the economizer by venting the zone of greater pressure to a zone of lower pressure.

Other objects and features of the invention will be apparent upon a consideration of the ensuing specification and drawings wherein:

FIGURE 1 is a diagrammatic representation of a refrigeration machine in an air conditioning system wherein the machine is equipped with a control of the type forming the subject of this invention;

FIGURE 2 is a partial perspective view of a portion of the evaporator and economizer of the refrigeration system shown in FIGURE 1 wherein certain parts are broken away in the interest of clarity.

FIGURE 3' is a view partly in elevation and partly i section illustrating the control valve used in the invention. 7

FIGURE 4 is a diagrammatic view of a refrigerationmachine equipped with a modified form of a control arrangement illustrating the invention.

For the'purpose or illustrating the invention, an air con ditioning system is diagrammatically illustrated in-FIG URE 1. The system, includes a refrigeration machine ineluding a motor compressor unit 10 comprising 'a centrifugal compressor 11 and a hermetic motor'12 arranged to drive the compressor; Gaseous refrigerant in the refrigeration system is compressed bythe compressor 11 and forwarded through discharge line 13 to a condenser 14 where it is liquefied as it passes in heat transfer relation 'with' a condensing medium such as water flowing in a 'closed circuit including coil 29, pump and cooling economizer 16 where it' is sub'jected to a reduction in pressure causing portions of the liquid refrigerant to flash '1 off or.vaporize and cool the remaining body of liquid refrigerant. The cooled liquid refrigerant then flows from line 17 to; theevaporator 18 which has assembled therein a coil 30 forming a part of a chilled water circuit, to be later described. As heat is extracted from the water in the coil 30 the liquid refrigerant is vaporized and flows throughsuction line 19 to the compressor to complete the refrigerant circuit. r e t V V As indicated above, a chilled water circuit includes coil 30 together with piping and a variable load represented at 40 which may beja unit comprising a coil for the dew of the chilled water and a fan for the purpose of providing a supply of room air over the coil to reduce the temperaeffects described above.

ture of the room air for eventual recirculation to the room. i

In extracting heat from the room air the water leaving the unit 49 has its temperature increased. The water is thendelivered by the pump 41 to the coil for the purpose of reducing its temperature. Theapparatus described is conventional and has enjoyed .widespreaduse in air conditioning system for a substantial period of time.

Referring to the economizer construction, it will be observed that the economizer 16 is divided into an upper high side and low side pressure. As the liquid flows into the chamber 26 portions thereof will -vaporize and the vapor so created is utilized to cool the motor 12 by provid- .ing a path for its flow through line 30' from the economizer chamber to the motor casing.

' economizer gas flows in heat transferwith the motor, it is delivered to the compressor at an intermediate stage of After :the

compression through line 31 having a damper 33 responsive to a difference in pressure between the evaporator 7 and the economizer. The purpose of this valve istojmaintain a sufiicient pressure within the motor chamber; This 41 a tendency is overcome, liquid refrigerant could fiow'in the line 30 intothe motor casing and cause the harmful To overcome the tendency of fiow in this direction, applicant provides in the side of his cooler a movable fiap member which is weighted and designed so as to open in the manner ofa check valve in response to a predetermined relation between the economizer and evaporator'pressure. In other words, once the evaporator pressure exceeds the economizer pressure the member 50 will open causing the pressure in the evaporator to be reduced and the'pressure in the economizer to increase. Thus, the tendency for the liquid refrigerant to flow from the evaporator to the economizer is overcome.

The member 50 illustrated in detail in FIGURE 3 includes mounting plate 60 having an opening 61 welded to a portion of the cooler, a flexible member 62 formed of neoprene secured to the mounting plate 60, a clamping plate 63 and a support plate 64. The latter two are connected to the flexible member 62 to provide rigidity to the assembly. The parts are designed so as to: swing pivotally about fasteningelements 65 in response to a predetermined difference in pressure between the gas on the opposite sides of the member 50. I

In FIGURE 4 there is illustrated a second embodiment of'the' invention; The refrigeration machine illustrated in FIGURE 4 is substantially identical to the machine illustrated in FIGURE 1. Reference numerals indicatingjcertain parts inFIGURE'l are 'used toidentify the corresponding parts shown in FIGURE-4. In the em bodiment illustrated in FIGURE 4, line 57 connects the evaporator directly with the condenser, Flow of refrigerant through line 57 is under the control of a valve member structurally and functionally similar to thatillustrated at50 in FIGURE 1. In the operation of the embodiment illustrated in FIGURE 4, a, pressure in the evaporator which'is in excess of the pressure in the condenser causes refrigerant to flow through line 57 thus building up pres- 'I evaporator.

sure in the condenserv while reducing the pressure in the Once a more normal pressure relationship between condenser and evaporator is obtained the tendency for refrigerant flow from theevaporator 18 to the economizer 16 is overcome and flow of refrigerant from the condenser to the evaporator is assured.

Asindicated above this invention is operative under circumstances where unusual pressure conditions exist within the refrigeration system. The unusual pressure relationships are brought about by temperature differences in the media supplied to the condenser and evaporator for the purpose of liquefying and vaporizing respectively, the refrigerant. To fully accomplish the ef'n ciencies available withthe control schemes presented the pumps 20 and 41 should be energized to cause flow within 51 will occur and a refrigerating efiect achieved.

particular control forms the subject of the United States patent application Serial No. 620,129, filed November 2, '1956, now issued as United States Letters Patent 2,921,446, and assigned to the assignee of' this invention. -As pointed out above,-there are circumstances during which time the water flowing in the condenser cooling 'water circuit may encounter a substantial 'reductionin of course, there is .a tendency forthe liquid refrigerant which has collected in the economizer, to fiow in a directron-opposite its normal intended. direction.- Unless such While we have described a preferred embodiment of our invention, it will be understood our invention is not limited thereto, since it may be otherwise embodied within the scope of thefollowing claims.

We claim: 7 V, v

1. Refrigeration apparatus comprising a compressor, a condenser, an economizer, an; evaporator a line connecting the economizer and the evaporator to pass liquid refrigerant to said evaporator, means providing an additional passage between the evaporator and economizer and .meansnormally closing said passage, said last-mentioned means being operative in response to a predetermined difference in pressure between the economizer and the evaporator to open said passage toreduce the pressure in the evaporator and increase the pressure in the economizer. a V

2. The invention set forth in claim 1 including a motor including a casing operating said compressor, a line confor the flow of gaseous refrigerant formed in the economizer to the casing to cool the motor.

3. The invention set forth in claim 2 including a line connecting the casing and the compressor providing a path of flow for gaseous refrigerant flowing through the motor casing.

4. The method of operating a refrigeration machine including a compressor, a condenser, an economizer and a cooler connected to form a circuit for the flow of refrigerant, which consists in the steps of supplying gaseous refrigerant to the condenser for liquefaction therein, forwarding the refrigerant to the economizer wherein portions of the liquid refrigerant vaporize and cool the remaining liquid refrigerant, delivering the cooled liquid refrigerant to the evaporator for conversion to the gaseous state and reducing the evaporator pressure by automatically venting the evaporator to the economizer in response to a predetermined pressure relationship between the evaporator and the economizer.

References Cited in the file of this patent UNITED STATES PATENTS 2,041,045 Carrier et a1 May 19, 193-6 2,164,761 Ashley July 4, 1939 2,249,882 Buchanan July 22, 1941 2,274,391 Zwickel Feb. 24, 1942 2,277,647 Jones Mar. 24, 1942 2,888,809 Rachfal June 2, 1959 2,916,893 Kramer Dec. 15, 1959 

